Soybeans are an important global source of protein and oil. Soy protein serves primarily as an animal feed containing all of the essential amino acids. In 2011, soybeans represented 56 percent of the worldwide oil seed production. Soybeans along with corn represent the two most important crops in the United States.
Soybean plants are vulnerable to a wide range of bacterial, fungal, viral, and parasitic diseases. A fungal disease called Asian Soy Rust or ASR has been rapidly spreading throughout the world. The fungus causing this disease is Phakopsora pachyrhizi. The disease is characterized by small tan-colored lesions to forming on the lower surface of the leaf. The lesions release spores into the wind. The wind carried spores have been reported to travel four hundred miles in a day. Originating in Asia, the disease spread to Africa in 1997, South America in 2001, and to the United States in 2004.
A timely response is needed to combat the threat of Asian Soybean Rust. Fungicide applications can prevent significant yield loss. Commercial germplasm in the U.S. and much of the world lacks resistance to Asian Soybean Rust, and the development of disease resistant cultivars provides another line of defense. There are currently five known dominant resistance genes in soybean known as Rpp1, 2, 3, 4, and 5.